1. Field of the Invention
The present invention relates generally to a portable charger for a mobile phone (also referred to as a mobile communication terminal or a portable phone) and, more particularly, to a portable charger for a mobile phone, which is easy to carry, can easily charge the battery of the mobile phone with direct current power charged in a secondary battery, and can simultaneously charge the secondary battery and the battery of the mobile phone using a travel adaptor.
2. Description of the Related Art
A conventional portable charger equipped with an internal battery is disclosed in Korean Utility Model Registration No. 20-0275514 (registered on May 1, 2002).
In the portable charger equipped with an internal battery, which is disclosed in Korean Utility Model Registration. No. 20-0275514, an Alternating Current (AC) power connection unit 110 provided with a power plug 111 is attached to a side of a body 100 to allow the portable charger to be connected to a domestic power outlet, as shown in FIGS. 1 and 2.
The power plug 111 can be retracted to a position parallel to the body 100 using a rotation shaft 112 provided on the body 100, so that it is secured in a position perpendicular to the body 100 when in use (indicated by dotted lines), and is retracted into a recess 113 when not in use (indicated by solid lines).
A cable 151 and an interface jack 152 are provided on a side of the body 100 to allow the charger to be electrically connected to the interface connector (not shown) of a mobile phone. The internal terminals of the interface connector of the mobile phone are electrically connected to the positive (+) terminal, negative (−) terminal and identification data input (IN) terminal of an external battery connection unit 115.
As shown in FIG. 2, the charger is electrically connected to domestic 110V or 220V AC power through the AC power connection unit 110. An ElectroMagnetic Interference (EMI) filter 121 is connected to the AC power connection unit 110 to remove noise from AC power that is applied through the AC power connection unit 110. A rectifying unit 122 is connected to the EMI filter 121 to rectify the AC power, applied through the EMI filter 121, to Direct Current (DC) power and supply the DC power to a switching mode power supply unit 114.
The switching mode power supply unit 114 functions to receive the DC current from the rectifying unit, interrupt the DC current according to a duty ratio, and supply stepped-down charging current. The switching mode power supply unit 114 includes a coil unit 114a for producing the stepped-down current by interrupting the DC current input from the rectifying unit 122, and a switching control unit 114b for adjusting the amount of charging current flowing into the secondary battery by switching the coil unit 114a. 
The external battery connection unit 115 is connected to the interface connector of the mobile phone so that identification data (ID) transmitted from the battery identification terminal of the mobile phone is applied to a microprocessor 119 through an identification output terminal OUT. The interface jack 152 is provided with the positive (+) input terminal, the negative (−) input terminal and the identification data input (IN) terminal that are connected to the charging terminal, ground terminal and identification terminal of the battery of the mobile phone, respectively.
In FIG. 2, a Pulse Width Modulation (PWM) control unit 116 adjusts the voltage level of current charging voltage based on a voltage control signal applied from the microprocessor 119 so that charging voltage applied to the external battery connection unit 115 reaches a specific reference voltage and is maintained at the specific reference voltage. The modulation signal output terminal of the PWM control unit 116 is connected to the base terminal of a transistor Q1, the output terminal of the switching mode power supply unit 114 is connected to the collector terminal of the transistor Q1, and the charging current input terminal of the external battery connection unit 115 as well as the voltage feedback signal input terminal of the PWM control unit 116 are connected to the emitter terminal of the transistor Q1.
An internal battery 117 connected to the output terminal of the switching mode power supply unit 114 is a secondary battery that stores electrical energy using DC power, output from the switching mode power supply unit 114, as charging current. The internal battery 117 is charged with electricity to charge an external battery (battery of a mobile phone) that is connected to the external battery connection unit 115.
The internal battery 117 is equipped with an overcharge prevention circuit to prevent overcharge. A photocoupler 118 is connected between the microprocessor 119 and the switching control unit 114b of the switching mode power supply unit 114 to convert a current control signal, applied by the microprocessor 119, into an optical signal, to convert the optical signal into an electrical signal having a specific duty ratio and to control the application of power to the switching mode power supply unit 114.
In the above case, when the battery of a mobile phone is connected to the external battery connection unit 115, the microprocessor 119 reads the identification data of the battery transmitted from the external battery connection unit 115, sets the maximum charging voltage and maximum charging current, and controls the switching mode power supply unit 114 and the PWM control unit 116 based on the maximum charging voltage and the maximum charging current.
In the case where a user charges the battery of a mobile phone with domestic 110V or 220V AC power, the user inserts the power plug 111 of the AC power connection unit 120 into a domestic power outlet and connects the interface jack 152 to the interface connector (not shown) of the mobile phone.
While the AC power flowing through the AC power connection unit 110 passes through the EMI filter 121, noise is filtered out from the AC power. The noise-free AC power is rectified to DC power by the rectifying unit 122, and the DC power is applied to the switching mode power supply unit 114.
The DC power applied to the switching mode power supply unit 114 is used to charge the battery of the mobile phone and the internal battery 117 under the control of the microprocessor 119.
After applying a current control signal, that is, a PWM modulation signal, to the photocoupler 118 based on the preset maximum charging voltage and charging current of the internal battery 117, the microprocessor 119 reads the identification data (ID) of the mobile phone transmitted from the external battery connection unit 115, sets the maximum charging voltage and maximum charging current for the battery of the mobile phone, and sets the reference voltage of the PWM control unit 116 to the maximum charging voltage of the battery of the mobile phone.
The photocoupler 118 outputs an electrical signal having a specific duty ratio to the switching control unit 114b to correspond to the current control signal transmitted from the microprocessor 119. The switching control unit 114b adjusts the amount of charging current, which will be supplied to the external battery connection unit 115 and the internal battery 117, by interrupting the operation of the coil unit 114a according to the duty ratio of the electrical signal.
The PWM control unit 116 compares the voltage (current charged voltage of the battery of the mobile phone), applied to the emitter terminal of the transistor Q1 and the connection node of the external battery connection unit 115, with the preset reference voltage, and adjusts the period of ON/OFF operation of the transistor Q1 so that the current charged voltage reaches the preset reference voltage and is maintained at the preset reference voltage.
When the current charged voltage reaches the reference voltage, the PWM control unit 116 indicates to the microprocessor 119 that current charged voltage has reached the reference voltage. The microprocessor 119 applies a current control signal to the photocoupler 118 in response to the information so that the amount of charging current output from the switching mode power supply unit 114 gradually decreases.
That is, the microprocessor 119 controls the operation of the switching mode power supply unit 114 according to the preset maximum charging voltage and current for the internal battery 117. Furthermore, the microprocessor 119 prevents overcharge of the battery connected to the external battery connection unit 115 by adjusting the amount of charging current that is output from the switching mode power supply unit 114 based on the current charged voltage of the mobile phone. When the internal battery 117 reaches a fully charged state, the microprocessor 119 detects the fully charged state using the overcharge prevention circuit and automatically blocks the inflow of charging current.
According to the above-described operation, the charging current output from the switching mode power supply unit 114 charges the internal battery 117 through a diode D1, and is applied to the external battery connection unit 115 and charges the battery of the mobile phone as well.
An operation of charging the battery of a mobile phone with charging power charged in the internal battery 117 is described below.
When the interface jack 152 of FIG. 1 is connected to the interface connector of the mobile phone in the case where the internal battery 117 has been charged through the above-described operation and the mobile phone must be charged at a location where domestic AC power is not available, part of the charging power is supplied through an operating power supply circuit as operating power.
At this time, the microprocessor 119 reads the identification data (ID) of the battery of the mobile phone transmitted from the external battery connection unit 115, sets the maximum charging voltage and current of the battery of the mobile phone, and sets the reference voltage of the PWM control unit 116 to the maximum charging voltage.
The PWM control unit 116 charges the battery of the mobile phone by comparing the current charged voltage of the battery of the mobile phone, connected to the external battery connection unit 115, with the preset reference voltage, and adjusting the period of ON/OFF operation of the transistor Q1 so that the current charged voltage reaches the preset reference voltage and is maintained at the preset reference voltage.
Although the conventional portable charger equipped with an internal battery is capable of charging the battery of a mobile phone even at locations where domestic AC power and automobile battery power are not available, the conventional charger is disadvantageous in that the conventional charger is not possible and the charging operation of the conventional charger is complicated and inconvenient because the cable 152, provided with the interface jack 152 that will be connected to the interface connector of a mobile phone, is required to charge the battery of the mobile phone and one end of the cable 152 must be electrically connected to the body 100.